Conventionally, there is an apparatus for performing encryption and decryption using a cryptographic key. For example, if a program to be encrypted is falsified, the apparatus makes it impossible for the program to be encrypted, thereby preventing unauthorized encryption.
However, a further improvement of security is demanded, and therefore, a new technique for improving security is needed.
Therefore, it is an object of an exemplary embodiment to provide a novel cryptographic processing apparatus, a novel cryptographic processing system, and a novel cryptographic processing method.
To achieve the above object, the exemplary embodiment can employ, for example, the following configurations. It should be noted that it is understood that, to interpret the descriptions of the claims, the scope of the claims should be interpreted only by the descriptions of the claims. If there is a conflict between the descriptions of the claims and the descriptions of the specification, the descriptions of the claims take precedence.
In an exemplary configuration of a cryptographic processing apparatus according to an exemplary embodiment, a cryptographic processing apparatus encrypts and decrypts data. The cryptographic processing apparatus includes a key data storage area, a mode setting circuit, and a process limitation circuit. In the key data storage area, a plurality of pieces of key data used for encryption and/or decryption are stored. The mode setting circuit sets, for at least one of the plurality of pieces of key data stored in the key data storage area, a process mode of either of an encryption process and a decryption process in association with the key data. The process limitation circuit receives a mode specifying command for specifying a process mode in association with key data from another apparatus, and if the received process mode and the process mode associated with the key data set in the mode setting circuit coincide with each other, permits the process in the process mode using the key data.
Based on the above, a process mode of either of an encryption process and a decryption process is set in association with at least one piece of key data. Thus, it is possible to achieve a novel cryptographic process for limiting a process mode using the key data to one of the encryption process and the decryption process.
In addition, the key data associated with the process mode of either of the encryption process and the decryption process may be key data of a common key that can be used in the encryption process and the decryption process.
Based on the above, it is possible to achieve a novel cryptographic process for limiting a process mode using key data of a common key to one of the encryption process and the decryption process.
In addition, the key data may be written to the key data storage area when the cryptographic processing apparatus is started. The mode setting circuit may set a process mode corresponding to the written key data when the cryptographic processing apparatus is started.
Based on the above, key data and a process mode corresponding to the key data are set at the start. Thus, it is possible to prevent another apparatus from setting the key data and the process mode first, and perform a cryptographic process immediately after the start.
In addition, the key data may be written to the key data storage area by execution of secure system firmware. A process mode corresponding to the written key data may be set in the mode setting circuit by execution of the system firmware.
Based on the above, key data and a process mode corresponding to the key data are set by secure system firmware. Thus, it is possible to increase the security of the contents of the settings.
In addition, the system firmware may be a boot program stored in a boot ROM.
Based on the above, key data and a process mode corresponding to the key data are set by a boot program. Thus, it is possible to set the key data and the process mode at the start, and therefore possible to increase the security of the contents of the settings.
In addition, if the process mode specified by the received mode specifying command and the process mode set in the mode setting circuit do not coincide with each other, the process limitation circuit may erase the key data to be used in the process mode from the key data storage area.
Based on the above, the erasing of key data can prevent a process that is not permitted from being performed, using the key data.
In addition, if the process mode specified by the received mode specifying command and the process mode set in the mode setting circuit do not coincide with each other, the process limitation circuit may discard the mode specifying command.
Based on the above, it is possible to prohibit a process in a process mode that is not permitted.
In addition, the cryptographic processing apparatus may further include a dummy key data storage area. In the dummy key data storage area, dummy key data different from the plurality of pieces of key data is stored. In this case, if the process mode specified by the received mode specifying command and the process mode set in the mode setting circuit do not coincide with each other, the process limitation circuit may perform control for processing data in the process mode using the dummy key data in a processing circuit.
Based on the above, it is possible to prevent a process that is not permitted from being performed, using proper key data.
In addition, if the process mode specified by the received mode specifying command and the process mode set in the mode setting circuit do not coincide with each other, the process limitation circuit may refuse to receive data input to be processed in the process mode.
Based on the above, it is possible to prohibit input data from being processed in a process mode that is not permitted.
In addition, if the process mode specified by the received mode specifying command and the process mode set in the mode setting circuit do not coincide with each other, the process limitation circuit may output, as data processed in the process mode, data generated by a process different from the process of the processing mode.
Based on the above, it is possible to prevent proper data from being output in a process mode that is not permitted.
In another exemplary configuration of the cryptographic processing apparatus according to the exemplary embodiment, the cryptographic processing apparatus encrypts and decrypts data. The cryptographic processing apparatus includes a key data storage area, a mode setting circuit, and a process limitation circuit. In the key data storage area, key data used for encryption and/or decryption is stored. The mode setting circuit sets, for the key data stored in the key data storage area, a process mode of either of an encryption process and a decryption process in association with the key data. The process limitation circuit receives a mode specifying command for specifying a process mode from another apparatus, and if the received process mode and the process mode set in the mode setting circuit coincide with each other, permits the process in the process mode using the key data associated with the process mode.
Based on the above, a process mode of either of an encryption process and a decryption process is set in association with one piece of stored key data. Thus, it is possible to achieve a novel cryptographic process for limiting a process mode using the key data to one of the encryption process and the decryption process.
In addition, the exemplary embodiment may be carried out in the forms of a cryptographic processing system including the above circuits and a cryptographic processing method including operations performed by the above circuits.
According to the exemplary embodiment, a process mode of either of an encryption process and a decryption process is set in association with at least one piece of key data. Thus, it is possible to achieve a novel cryptographic process for limiting a process mode using the key data to one of the encryption process and the decryption process.
These and other objects, features, aspects and advantages of the exemplary embodiments will become more apparent from the following detailed description of the exemplary embodiments when taken in conjunction with the accompanying drawings.